Sorta. There's two ways of using it though. If you ask me "surely you don't think the rational response is to flinch away like she's doing!?" I'd shrug and say "nah". If you put me on the spot and asked "would you say she's being 'irrational'? Yes or no?", I'd say "sure, you can say that I guess". It can be functional short hand sometimes, if you make sure that you don't try to import connotations and use it to mean anything but "suboptimal", but the term "suboptimal" captures all of that without hinting at false implications. Normally when you actually understand why someone is doing something but think it won't work, you use other words. For example, Bob went to the grocery store to buy food because he thinks they're open. They're not. Do you say he's "irrational" or just wrong. I dunno about you, but using "irrational" there doesn't seem to fit.

Often, however, it's used when you think you understand why they're doing something - or when you understand the first layer but use it as a stop sign instead of extending your curiosity until you have a functional explanation. Example: "She's screaming at her kids even though it isn't going to help anything. I understand why she does it, she's just angry. It's irrational though". Okay, so given that it's not working, why is she letting her anger control her? That's the part that needs explaining, because that's the part that can actually change something. If the way you're using "irrational" leads you to even the temptation to say "you're being irrational", then (with a few cool exceptions) what it really means is that you think you understand all that there is to understand, but that you're wrong.

For example, Bob went to the grocery store to buy food because he thinks they're open. They're not. Do you say he's "irrational" or just wrong.

"Irrational" implies making a bad choice when a good choice is available. If Bob was mistaken, he was just mistaken. If he knew he could easily check the store hours on his phone but decided not to and spent 15 minutes driving to the store, he was irrational.

Example: "She's screaming at her kids even though it isn't going to help anything. I understand why she does it, she's just angry. It's irrational though". Okay, so given that it's not working, why is she letting her anger control her?

Because she is dumb and unable to exercise self-control.

It seems to me you just don't like the word "irrational". Are there situations where you think it applies? In what cases would you use this word?

"Irrational" implies making a bad choice when a good choice is available. If Bob was mistaken, he was just mistaken. If he knew he could easily check the store hours on his phone but decided not to and spent 15 minutes driving to the store, he was irrational.

It seems like you’re burying a lot of the work in the word “available”. Is it “available” if it weren’t on his mind even if he could answer “yes, it would be easy to check” when asked? Is it “available” when it’s not on his mind but reminding him wouldn’t change his decision, but he has other reasons for it? If he doesn’t have other reasons, but would do things differently if you taught him? If a different path were taken on any of those forks?

I can think of a lot of different ways for someone to "know he could easily check store hours" and then not do it, and I would describe them all differently - and none of them seem best described as “irrational”, except perhaps as sloppy shorthand for “suboptimal decision algorithm”.

Because she is dumb and unable to exercise self-control.

That’s certainly one explanation, and useful for some things, but less useful for many others. Again, shorthand is fine if seen for what it is. In other cases though, I might want a more detailed answer that explains why she is “unable” to exercise self control - say, for example, if I wanted to change it. The word “irrational” makes perfect sense if you think changing things like this is impossible. If you see it as a matter of disentangling the puzzle, it makes less sense.

It seems to me you just don't like the word "irrational". Are there situations where you think it applies? In what cases would you use this word?

It’s not that I “don’t like” the word - I don't “try not to use it” or anything. It’s just that I’ve noticed that it has left my vocabulary on its own once I started trying to change behaviors that seemed irrational to me instead of letting it function as a mental stop sign. It just seems that the only thing “irrational” means, beyond “suboptimal”, is an implicit claim that there are no further answers - and that is empirically false (and other bad things). So in that sense, no, I’d never use the word because I think that the picture it tries to paint is fundamentally incoherent.

If that connotation is disclaimed and you want to use it to mean more than “suboptimal”, it seems like “driven by motivated cognition” is the probably one of the closer things to the feeling I get by the word “irrational”, but as this post by Anna shows, even that can have actual reasons behind it, and I usually want the extra precision by actually spelling out what I think is happening.

If I were to use the word myself (as opposed to running with it when someone else uses the word), it would only be in a case where the person I’m talking to understands the implicit “[but there are reasons for this, and there’s more than could be learned/done if this case were to become important. It’s not]”

EDIT: I also could conceivably use it in describing someone's behavior to them if I anticipated that they'd agree and change their behavior if I did.

I don't know why you let it function as a stop sign in the first place. "Irrational" means neither "random" nor "inexplicable" -- to me it certainly does not imply that "there are no further answers". As I mentioned upthread, I can consider someone's behaviour irrational and at the same time understand why that someone is doing this and see the levers to change him.

The difference that I see from "suboptimal" is that suboptimal implies that you'll still get to your goal, but inefficiently, using more resources in the process. "Irrational", on the other hand, implies that you just won't reach your goal. But it can be a fuzzy distinction.

As I mentioned upthread, I can consider someone's behaviour irrational and at the same time understand why that someone is doing this and see the levers to change him.

If "irrational" doesn't feel like an explanation in itself, and you're going to dig further and try to figure out why they're being irrational, then why stop to declare it irrational in the first place? I don't mean it in a rhetorical sense and I'm not saying "you shouldn't" - I really don't understand what could motivate you to do it, and don't feel any reason to myself. What does the diagnosis "irrational" do for you? It kinda feels to me like saying "fire works because phlogistons!" and then getting to work on how phlogistons work. What's the middle man doing for you here?

With regard to "suboptimal" vs "irrational", I read it completely differently. If someone is beating their head against the door to open it instead of using the handle, I woudln't call it any more "rational" if the door does eventually give way. Similarly, I like to use "suboptimal" to mean strictly "less than optimal" (including but not limited to the cases where the effectiveness is zero or negative) rather than using it to mean "less than optimal but better than nothing"

Because for me there are basically three ways to evaluate some course of action. You can say that it's perfectly fine and that's that (let's call it "rational"). You can say that it's crazy and you don't have a clue why someone is doing this (let's call it "inexplicable"). And finally, you can say that it's a mistaken course of action: you see the goal, but the road chosen doesn't lead there. I would call this "irrational".

Within this framework, calling something "irrational" is the only way to "dig further and try to figure out why".

With regard to "suboptimal" vs "irrational", I read it completely differently.

Interesting. I dig into plenty of things before concluding that I know what their goal is and that they will fail, and I don’t see what is supposed to be stopping me from doing this. I’m not sure why “I don’t [yet] have a clue why” gets rounded to “inexplicable”.

Outcome? I was going to say that suboptimal could refer to a case where we don't know if you'll reach your goal, but we can show (by common assumptions, let's say) that the action has lower expected value than some other. "Irrational" does not have such a precise technical meaning, though we often use it for more extreme suboptimality.

Yes, outcome. Look at what each word is actually describing. Irrationality is about process. Suboptimal is about outcome -- if you inefficiently but reliably calculate good strategies for action, that's being slow, not suboptimal in the way we're talking about, so it's not about process.